class calcu{private System.Windows.Forms.Button but1;private System.Windows.Forms.Button but2;private System.Windows.Forms.Button but3;....private System.Windows.Forms.Button butequel;private void but_Click(object sender, System.EventArgs e){ if(sender == but1)
textbox.text +=1; else if(sender == but2) textbox.text +=2; else if(sender == but3) textbox.text +=3; else textbox.text = result; }}